The invention relates to fuel filters and more specifically to an in-tank fuel filter and method of making same wherein the fuel line fitting comprises a pair of mating segments which are bonded to the fabric and to each other.
In conventional vehicular fuel systems, a fuel filter is provided at the terminus of the fuel line within the fuel tank. The in-tank filter functions as a large area filter possessing several significant benefits. First of all, because the filter is generally enveloped by the fuel, its large surface area provides minimal flow resistance. Secondly, because the fuel flow is intermittent, that is, related to the operation or quiescence of the vehicle engine, particulates attracted to and trapped on the surface of the filter during periods of fuel flow will generally dislodge during quiescent periods. Such action effectively renews the filtration surface and extends the life of the filtration element to the extent that it generally never requires replacement. Thirdly, certain materials such as fabric manufactured from Saran brand threads (Saran is a registered trademark of the Dow Chemical Company.) exhibit the capability, when wetted with gasoline, of separating water from gasoline and thus inhibit the flow of water into the fuel system of the vehicle.
Numerous in-tank fuel filter designs have been proposed. For example, in U.S. Pat. No. 3,826,372, granted Jul. 30, 1974, a tubular flexible filter is disclosed. The filter is secured to a fuel line fitting and is maintained in forced contact with the tank bottom to assure a flow of fuel at the lowest possible fuel level in the tank.
Another in-tank fuel filter is disclosed in U.S. Pat. No. 4,312,753. This device utilizes a flexible woven plastic cloth having spacers secured to at least one of the walls of the filter to inhibit collapse of the filter and ensure fuel flow therethrough. The filter includes a fuel line fitting which is injection molded onto the filter fabric.
A common difficulty of these and other fuel filter designs relates to the incompatibility of materials utilized to fabricate the filter. For example, as noted above, the filter fabric may be of Saran material. A common and desirable material for the fittings of the filter such as the fuel line coupling and spacers is nylon. If, as discussed above, the fittings are injection molded onto the fabric, no melting and molecular bonding of the materials typically occurs. Accordingly, achieving a strong mechanical bond may be difficult, in the first place. In the second place, it may be difficult to achieve an impervious seal between the fabric and the fitting which precludes flow of any unfiltered fuel into the fuel system.
A second area of difficulty relates to the injection molding process. In such a process, a swatch of fabric having a previously prepared, suitably sized opening is positioned within a mold. The mold is closed and the fitting, spacer or other component of the filter is then injection molded according to conventional techniques. While the process itself is viable and the products fabricated thereby are wholly serviceable, utilization of injection molding for the production of items such as fuel filters is not without difficulties. The first problem relates to handling the fabric. Because of the difficulties of handling fabric swatches, such as, engagement, movement and orientation, for example, handling of the individual fabric swatches by automated equipment poses many challenges. Accordingly, manual handling of the fabric presently provides the highest production yield. A second, associated problem relates to placement of the fabric within the mold. The fabric must be accurately positioned within the mold cavity in order to ensure fabrication of an acceptable component. As those familiar with injection molding processes will readily appreciate, the inaccurate placement of components within a mold cavity which then prevents the mold from properly closing and sealing during the injection molding process results in a wholly unacceptable condition which produces a defective product and may result in material loss. Though slower than automated equipment, manual placement of the fabric in the mold cavity is presently preferable.
A third area of difficulty devolves from the injection molding process and another aspect of fabric position. As the molten material is injected into the mold cavity and against the fabric, it tends to displace the fabric against a cavity wall. Consequently, the spacer or other molded fitting will not be medially positioned on the fabric but may reside substantially or entirely on one side of the fabric which is undesirable. It is known to include slender, aligned, positioning pins in the mold which retain the fabric in the desired position during molding. Such pins increase the complexity of the mold, add to its expense and are easily damaged. Furthermore, the openings they leave in the molded component may permit unfiltered fuel flow into the interior of the fuel filter.
Accordingly, products and processes which represent improvements over the injection molding process routinely utilized for the production of items such as fuel filters are not only desirable but possible.